The Angiotensin Converting Enzyme (ACE) CSF test measures ACE levels in cerebrospinal fluid, primarily to help diagnose Neurosarcoidosis, a serious inflammatory condition affecting the brain/spine, as elevated levels often signal granuloma formation by immune cells (macrophages). While useful, it’s not definitive and must be interpreted with other tests (like imaging and blood work) as high levels can also appear in other infections or tumors, but it helps differentiate sarcoidosis from other neurological issues